In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
U.S. Pat. No. 5,593,254 shows a cutting insert for a milling tool formed for the hobbing of workpieces having cogs, such as gear wheels, racks and the like. The milling tool comprises a tool body that defines a rotation axis and should have a fixing end, an opposite outer end, and a peripheral surface that extends around the rotation axis between the fixing end and the outer end. The tool body comprises a large number of seats that are arranged one after the other. The cutting insert, which is arranged in one of said seats, comprises an under side, an opposite upper side that forms a chip surface and extends parallel to an extension plane, and a circumferential edge side that connects the upper side and the under side. A centre axis extends through the under side and the upper side and a symmetry line is perpendicular to and intersects the centre axis. A first cutting edge comprises a primary main cutting edge, a secondary main cutting edge—which are symmetrical in respect of the symmetry line and formed where the edge side meets the chip surface—and a transverse end cutting edge that extends between the primary main cutting edge and the secondary main cutting edge. The cutting insert is fastened by a screw that extends through an eccentric hole through the cutting insert. The cutting insert has a ridge on the under side that is in engagement with a groove in the seat. The cutting insert has a negative cutting geometry, which makes it necessary to arrange the cutting insert so that the chip surface leans in relation to a radial plane in respect of the rotation axis. This causes an error of the involute of the cogs that are to be milled.
EP-A-2 072 162 shows another cutting insert for a milling tool formed for the hobbing of a workpiece having cogs, such as gear wheels, racks and the like. The cutting insert comprises a row of three teeth. Each tooth is formed for engagement with a gash of the workpiece. The cutting insert has an upper side that forms a chip surface for each tooth. The chip surfaces of the three teeth are lying in a common plane, which means that a normal of the chip surface will form an acute angle with a tangent of the helix line, along which the teeth are arranged and where this intersects the chip surface at least for two ones of the teeth. The chip surface for each tooth leans downward from the end cutting edge but is perpendicular to the edge sides along the main cutting edges, which gives a negative cutting geometry along the same.
JP-A-2001-353621 shows another cutting insert for a milling tool for hobbing. This cutting insert is formed with a row of teeth.